Newer birth control pills raise the risk of a blood clot by as much as or more than older formulations, researchers report — but the risk is still very low.
The study found that women taking some of the newer formulations had about four times the risk of a blood clot, called venous thromboembolism or VTE, as a woman not taking any birth control pill.
But the overall risk is still very low — just 14 cases out of every 10,000 women — the researchers report in the BMJ, the online journal of the British Medical Association.
That’s far lower than the risk of being pregnant. Pregnant women have 10 times the risk of a blood clot. That’s because estrogen — contained in most birth control pills — makes the blood more likely to clot, says Dr. Barbara Levy, vice president for health policy for the American College of Obstetricians and Gynecologists (ACOG).
According to a story published in NBC Health News, doctors have known for years that some of the newer contraceptives carry a higher risk of blood clots than older ones do. It’s not clear why, but the newer formulations use a different type of a second hormone, called progesterone or progestin.
Yana Vinogradova of Britain’s University of Nottingham and colleagues looked at data from 10,000 women across Britain. About half of them had been diagnosed with a blood clot.
ACOG says doctors should consider an individual woman’s risk of blood clots before prescribing any formulation of birth control pill.
Risk factors include smoking, being over 35, having major surgery that keeps a woman in bed for a long time, lupus and inflammatory bowel disease.
Source: The Gaurdian